Method for coloring fruits and vegatables

ABSTRACT

The color of fruits and vegetables is enhanced by applying thereto a compound which has the ability to cause the accumulation of lycopene in the tissues of the treated produce. Examples of compounds used in accordance with the invention are: 4-( Beta -(DIETHYLAMINO)-ETHOXY)-BENZALDEHYDE 4-( Beta -(DIETHYLAMINO)-ETHOXY)-BENZENE N,N-diethyl-ethanolamine Beta -(DIETHYLAMINO)ETHYL ANISOLATE

Unlted States Patent 1191 1111 3,911,149 Yokoyama et al. Oct. 7, 1975[54] METHOD FOR COLORING FRUITS AND 3,833,350 9/1974 Cooke et al.426/268 VEGETABLES [75] Inventors: Henry Yokoyama; Wan-Jean Hsu, FOREIGNPATENTS OR APPLICATIONS both of Pasadena; Stephen M. 681,032 2/1969Canada Poling, Seal Beach, all of Calif.

[73] Assignee: The United States of America as Primary Xamin N0rmanYudkoff represented by the Secretary of Assistant Examiner-Curtis P.Ribando Agriculture, Washington, DC, Attorney, Agent, or Firm-M. HowardSilverstein;

W'll" T' k' 22 Filed: 061. 9, 1974 l d [21] Appl. No.: 513,422

Related US. Application Data [57] ABSTRACT [62] 404980 1973 The color offruits and vegetables is enhanced by applying thereto a compound whichhas the ability to [52] U S Cl 426/268, 426/177 426/270 cause theaccumulation of lycopene in the tissues of l 426/3022, 426/377 426/379the treated produce. Examples of compounds used in 51 1m (:1 A2 3L 1/272accordance withhe invention are: 581 Field 61 Search 426/102, 177, 206,250, 44Bdiethylaminm'ethoxyl'benzaldehyde 426/252, 262, 268, 269, 270,308, 311, 377, l 379; 71/98, 108, 111, 121; 117/3 i FB-(d1ethylam1n0)ethyl anlsolate [56] References CitedN,N-diethyl-phenylpropylamine UNITED STATES PATENTS 3 Claims, No w g3,684,530 8/]972 Yokoyama 426/268 METHOD FOR COLORING FRUITS ANDVEGETABLES This is a division of our copending application, Ser. No.404,908, filed Oct. 10, 1973, now US. Pat. No. 3,864,501.

DEFINITIONS Various symbols used in this document are defined asfollows:

The abbreviations Et and Me refer to ethyl and methyl, respectively.

Lower alkyl means an alkyl radical containing 1 to 4 carbon atoms.Similarly, lower alkoxy means an alkoxy radical having I to 4 carbonatoms.

The symbol Ph designates the phenyl radical. The phenylene radical(C,,H.,) is depicted by the symbol 6. Where particular positions ofsubstituents are involved, this is designated by appropriate numbers.Thus indicates that the substituents are at the 1,4 positions, i.e.,para to one another.

DESCRIPTION OF THE INVENTION This invention relates to and has amoungits objects the provision of novel processes for coloring fruits andvegetables.

Further objects of the invention will be evident from the followingdescription wherein parts and percent ages are by weight unlessotherwise specified.

In the following description, the application of the invention to citrusfruits is stressed. It is to be understood that this particularembodiment of the invention is provided by way of illustration and notlimitation. In its broad ambit, the invention is applicable to all kindsof fruits and vegetables which contain carotenogenic tissues, that is,tissues which produce carotenoid pigments. Illustrative examples of suchfruits and vegetables are apricots, peaches, cherries, nectarines,tomatoes, bell peppers, chili peppers, carrots, sweet potatoes, etc., aswell as oranges, lemons, tangerines, grapefruit, and other citrusfruits.

It is well-known that one factor which influences the market value offruits and vegetables is the color thereof. It often happens that whenfruits and vegetables are received at the packing house, their color isdeficient even though they are entirely ripe and in excellent condition.This is particularly true with citrus fruit in which case, owing tovagaries in the. weather, position of the fruit on the tree, etc., theharvested fruit is often pale or non-uniform in color despite the factthat it is physiologically mature.

A principal object of the invention is to obviate the problem outlinedabove. The invention provides the means whereby the color of harvestedfruits and vegetables can be improved, for example, oranges ortangerines which are yellow or greenish can be provided with a richorange color.

Basically, the objects of the invention are attained by applying to thewhole harvested fruit or vegetables any of the components describedbelow.

Group I.

Compounds of the structure ll (A k)-Z H2),.

wherein:

Alk is lower alkyl, preferably methyl or ethyl. n is an integer from 2to 4. R is a member of the group consisting of H, lower al- 10 kyl,phenyl, CH CHPh, and CH CH- Group II.

[5 Compounds of the structure l )2 2)'|OC-0Alk wherein:

Alk is lower alkyl, preferably methyl or ethyl. n is an integer from 2to 4.

Group III.

Compounds of the structure (Alk) N(CH ),,O0R

wherein: 3o Alk is lower alkyl, preferably methyl or ethyl.

n is an integer from 2 to 4. R is a member of the group consisting of H,OH,

lower alkyl, and lower alkoxy.

Group IV.

Compounds of the structure wherein: 4O Alk is lower alkyl, preferablymethyl or ethyl.

n is an integer from 2 to 4.

Group V.

Compounds of the structure (Alk)- 2)O-Cd R wherein:

Alk is lower alkyl, preferably methyl or ethyl. n is an integer from 2to 4. R is a member of the group consisting of H, OH,

lower alkyl, and lower alkoxy.

Group VI.

Compounds of the structure wherein:

Alk is lower alkyl, preferably methyl or ethyl. m is an integer from 1to 5. R is a member of the group consisting of H, OH,

lower alkyl, and lower alkoxy.

Group VII.

Compounds of the structure wherein:

Alk is lower alkyl, preferably methyl or ethyl. is an integer from 3 to7.

Group VIII.

Compounds of the structure wherein:

Alk is lower alkyl, preferably methyl or ethyl.

n is an integer from 2 to 4. R is a member of the group consisting of H,lower alkyl, and phenyl.

The compounds of the invention operate not by any dyeing effect (theyare themselves essentially colorless), but by inducing the selectiveaccumulation of lycopene as the predominant pigment in the carotenogenietissue. Lycopene is the natural red coloring principle of the tomato,and its accumulation in the tissue causes an intensification of thecolor of the treated fruit or vegetable. Depending on the amount oflycopene formed, the treated produce will assume an orange or even a redcolor.

Contributing to the color enhancement obtained in the process of theinvention is that the applied compounds also increase the production (inthe treated tissue) of provitamins A, including 01-, 5-, and especiallyy-carotcne,

Since, the compounds of the invention are effective in very smallamounts, they are most conveniently applied in conjunction with an inertcarrier such as water, ethanol, isopropanol, or wax. A typical plan forcarrying out the treatment of the invention is to dip the fruit orvegetable in an aqueous or isopropanol solution containing a smallproportionfor example, about 0.1 to 1071 of any of the compoundsdescribed above. It is, of course, not essential to apply the solutionby dipping; it can be applied by spraying, flooding, or the like.

Since many fruits and vegetables have a natural waxy outer coating whichis water-repellent, it is preferred that the treating solution contain awetting agent so that the solution can uniformly coat the entire surfaceof the fruit or vegetable. For this purpose one may use any conventionalsurfactant such as soaps, sodium alkyl (C -C sulphates, sodium alkane (C-C sulphonates, sodium alkyl (C -C enzene sulphonates, esters ofsulphosuccinic acid such as sodium dioctylsulphosuccinatc, etc. Wettingand dispersing agents of the non-ionic type are suitable, for example,the reaction products of ethylene or propylene oxide with fatty acids,with polyhydric alcohols, with partial esters of fatty acids andpolyhydric alcohols, or with alkyl phenols, etc. Typical of such agentsare a polyoxyethylene stearate containing about 20 oxyethylene groupsper mole, a polyoxycthylene ether of sorbitan monolaurate containingabout 16 oxyethylene groups per mole, a distearate of polyoxyethylcncether of sorbitol containing about 40 oxyethylene groups per mole,isooctylphenyl ether of polyethylene glycol, etc. Generally, only asmall proportion of surfactant is used-on the order of 0.05 to 0.5%,based on the weight of solution. In addition to, or in place of thesurfactant, a supplementary solvent may be added to the primary solvent(water) in quantity sufficient to disperse the active agent. For suchpurpose one may use ethanol, isopropanol, or other inert volatilesolvent, particularly one which is at least partly miscible with water.It is evident that the solutions need not necessarily be true solutions;they may be colloidal solutions, emulsions, or suspensions, all of thesebeing considered as solutions for the purposes of the invention.

It may also be observed that some of the compounds of the inventionthosewith long alkyl chainsexhibit emulsifying activity and can be used inaqueous solution without any added wetting agent.

In the event that the compounds of the invention are applied in a waxcarrier, one may use for the purpose any wax, including hydrocarbonwaxes such as paraffin or microcrystalline petroleum wax; beeswax;carnauba wax; spermaceti; etc. The preparation will generally containabout 0.1 to 10% of any of the compounds described above, and may beapplied in various ways. One technique is to liquefy the preparation bywarming it and then applying it to the fruit or vegetable by dipping orspraying. Another plan is to dissolve the waxcontaining preparation inan inert volatile solvent such as hexane, octane, stoddard solvent,deodorized kerosene, or other volatile petroleum fraction and apply theresulting solution by spraying or dipping to the produce.

The action of the compounds is not immediate; the development of colorrequires some time for chemical reactions to take place within thetissue. Accordingly, after the step of applying the compound, thetreated produce is held so that the desired coloration will develop. Thetemperature at which the holding is conducted may varyfor example, fromabout 15 to about C .and influences the rate of coloration in that colorenhancement will take place more rapidly at the higher temperatures, andvice versa. Usually, for convenience it is preferred to conduct theholding at room temperature. Regardless of the temperature used, thetreated fruit or vegetable should have access to air during the holdingperiod so that it can respire and remain in a vital condition. The timerequired for color development in any particular case will varydepending on several factors including the type of fruit or vegetable,the particular compound used and the amount applied, the temperatureduring the holding period, the degree of color enhancement desired, etc.In many cases, excellent color development is obtained where treatedcitrus fruits are held for about 12-72 hours at ambient temperature.

When the desired color level has been attained, the fruit or vegetablemay be stored at conventional cold storage temperature (about 5l0 C.)until it is to be used. At such temperatures the established color isretained, and further color development is retarded. Storage under suchconditions can be applied for periods of up to 2 or 3 months withoutexcessive deepening of color or deterioration of the fruit or vegetable.

Since the enhancement of color in accordance with the invention involvesthe biosynthesis of lycopene within the fruit or vegetable tissue, it isobvious that the product to which the invention is applied be in a freshcondition, i.e., in a physiologically-active state so that it is capableof respiring and undergoing normal postharvest metabolic changes.

Where the compounds of the invention are applied to the surface offruits or vegetables, the coloration enhancement will take place in thepeel or rind of the treated product. If deeper color enhancement isdesired such as coloration of the flesh together with coloration of thepeel, the compounds are applied in such a way that they penetratethrough the peel. This can be done by vacuum infiltration. Thus thefruit or vegetable is placed in a vessel with an excess of a solutioncontaining a compound of the invention. The vessel is sealed and avacuum is applied and then released. This causes the solution topermeate the peel to the flesh within. The treated product is thenstored as described to develop the desired coloration.

Hereinabove we have stressed the application of the invention for thepurpose of enhancing the color of fruits and vegetables. Another phaseof the invention is concerned with the preparation of carotenoidpigments which may be used for coloring food products of all kinds. Aspecial advantage of these carotenoid pigments is that they are naturalconstituents of fruits and vegetables and thus can be safely used infoods. In practicing this phase of the invention, fruits or vegetables,or parts thereof are treated with any of the compounds described aboveand stored to develop substantial increase in color. The so-formedcarotenoid pigments are then isolated from the treated substrate byconventional means such as pressing or extraction with a solvent. In apreferred embodiment of this aspect of the invention, the procedure isapplied to the peels of oranges, lemons, grapefruit or other citrusfruit which are obtainable as waste from food processing plants. Thepeels are coated by spraying or dipping with an aqueous solutioncontaining about 0.1 to of any of the color-enchancing compounds hereindescribed. preferably, to attain good contact of the solution with thepeels, a small proportion of a wetting agent is incorpo rated therein.Also to retard mold growth or other microbial deterioration, it ispreferred that the solution contain a small proportion-for example,about 0.05 to 0. l%of a preservative such as sodium benzoate, so diumsorbate, or the lower alkyl esters of parahydroxybenzoic acid. The peelsare then allowed to stand at room temperature for several days (usuallyabout a week) until a strong color enhancement is attained. It is ofcourse obvious that since the development of carotenoids is based onbiochemical changes, the peel to which the process is applied should bein a fresh condition so that it constitutes a viable living systemcapable of further carotenoid biosynthesis. Also the peel should beexposed to air during the storage period so that respiration can takeplace. Following completion of the storage period, the peels are treatedas by pressing or extraction to recover the carotenoid pigmentstherefrom. Preferably the treated peel is extracted with a mixture ofequal volumes of isopropanol and acetone. The extract is then treated toevaporate the solvent, leaving as a residue the desired product-amixture of carotenoid pigments which will generally contain lycopene asthe principal pigment.

The invention is further demonstrated by the following illustrativeexample.

The compound used in this example was diethylaminoethyl anisolate Fruitsand vegetables were treated by dipping in or spraying with 5-10% (w/v)solutions of the compound in isopropanol, and then storing the treatedproduce at room temperature (about 2022 C.). For example, Marsh seedlessgrapefruit treated with a 10% solution of the compound developed a lightorange color within 2 days, and after 2 weeks the peel developed aboutug/g (dry basis) of lycopene. The orange color persisted for a muchlonger period of time than observed with the compounds of Group I.

Group V:

The compounds of this group can be synthesized by the procedure givenbelow, wherein Alk is lower alkyl, n is an integer from 2 to 4, and R isa member of the group consisting of H, OH, lower alkyl, and loweralkoxy.

The procedure is typified by the synthesis of diethylaminoethylanisolate.

One-tenth mole of Et NCH CH- OH in I00 ml. benzene was stirred in around bottom flask equipped with a dropping funnel and reflux condenser.Onetenth mole of in 50 ml. benzene was slowly added. The reactionmixture was refluxed for /2 hour, cooled in an ice-bath, and theprecipitate collected by filtration. The residual solution was washedwith water, and the benzene stripped off on the evaporator. The residuewas combined with the precipitate and treated with 5% aqueous NaOH whichcaused an oil to form. The oil was separated and the remaining solutionextracted with ether. The combined oil and ether extract was washed withwater and dried over anhydrous Na SO The ether was removed on theevaporator, yielding the desired product.

Having thus described the invention, what is claimed l. A process forenhancing the coloration of harvested fruits and vegetables whichcontain carotenogenic tissue, which comprises applying to the surface ofthe fruit or vegetable a compound of the structure

1. A PROCESS FOR ENCHANCING THE COLORATION OF HARVESTED FRUITS ANDVEGETABLES WHICH CONTAIN CAROTENOGENIC TISSUE, WHICH COMPRISES APPLYINGTO THE SURFACE OF THE FRUIT OR VEGETABLE A COMPOUND OF THE STRUCTURE 2.The process of claim 1 wherein the fruit or vegetable after applicationof the aforesaid compound is held at a temperature about from 15* to 35*C.
 3. The process of claim 1 wherein the stated compound